There have been known electronic devices in which a through hole is formed in a circuit board to have an opening on a pad. A plated layer is formed on the inner circumference surface of the through hole, and a circular resist is formed around the opening of the through hole to prevent solder from flowing into the through hole (see, for example, Patent Application Publication (KOKAI) No. 2008-226983).
This type of electronic devices are required to be capable of preventing solder from flowing into the through hole and also to have a structure such that trouble is less likely to occur.